Assigning code space to portable base stations

ABSTRACT

In addition to other aspects disclosed, a portable base station requests assignment of a portion of a code space from a remotely located control station. The assignment is based upon the location of the portable base station. The portable base station is also capable of transmitting an identification signal using the assigned code space portion to uniquely identify the portable base station to one or more access terminals.

BACKGROUND

This description relates to assigning portions of a code space toportable base stations.

Cellular communication systems include antenna towers erected in fixedlocations to provide wireless coverage to devices such as cellularphones, personal digital assistants (PDAs) and computer systems (each ofwhich is referred to as an Access Terminal or AT). In some situations anAT may be located within the coverage area of multiple towers. Todistinguish one tower from another, each tower transmits a uniqueidentification signal that includes information assigned to the tower.This information may be a sequence of pseudorandom numbers (PN) that aretransmitted in a repetitive manner. To uniquely identify each tower,transmission of the PN sequence is initiated from different elements inthe sequence or different sequences may be transmitted. Using one PNsequence, the starting elements may be identified by a number thatrepresents the offset from the first element in the sequence to thestarting element (assigned to the tower). Prior to becoming operational,different offsets may be assigned to the towers in a procedure known asradio frequency (RF) planning that seeks to protect against interferingidentification signals being transmitted from two or more closelylocated towers.

SUMMARY

In general, in some aspects of the invention, a portable base stationrequests assignment of a portion of a code space from a remotely locatedcontrol station. The assignment is based upon the location of theportable base station. The portable base station also transmits anidentification signal using the assigned code space portion to uniquelyidentify the portable base station to one or more access terminals.

The request from the portable base station may include data thatrepresents the location of the portable base station. The code space mayinclude a sequence of pseudorandom numbers and the assigned code spaceportion may be defined by an offset associated with the sequence. Thisoffset may be represented by one or more types of data such as by anumber of chips. Requesting the assignment may be initiated by apredefined event such as powering up the portable base station or theremotely located control station requesting the status of the portablebase station. The code space may conform to one or more standards andprotocols such as a Code Division Multiple Access (CDMA) standard, aUniversal Mobile Telecommunication System (UMTS) standard, or othersimilar standard.

In some aspects of the invention, a system is disclosed that includes aportable base station that requests assignment of a portion of a codespace from a remotely located control station. The assignment is basedupon the location of the portable base station. The portable basestation is also capable of transmitting an identification signal byusing the assigned code space portion to uniquely identify the portablebase station to one or more access terminals.

The portable base station may provide the functionality of a radio node,a radio node controller, an access gateway, and other similarcomponents. The assignment may be based upon the distance between theportable base station and another base station. The remotely locatedcontrol station may include a server for assigning the code spaceportions. The assignment request may include data that represents thelocation of the portable base station. The code space may include asequence of pseudorandom numbers and the assigned code space portion maybe defined by an offset associated with the sequence. This offset may berepresented by one or more types of data such as by a number of chips.Requesting the assignment may be initiated by a predefined event such aspowering up the portable base station or the remotely located controlstation requesting the status of the portable base station. The codespace may conform to one or more standards and protocols such as a CodeDivision Multiple Access (CDMA) standard, a Universal MobileTelecommunication System (UMTS) standard, or other similar standard.

In some aspects of the invention, a medium bears instructions to cause aportable base station to request assignment of a portion of a code spacefrom a remotely located control station. The assignment is based uponthe location of the portable base station. The instructions also causethe portable base station to transmit an identification signal using theassigned code space portion such that the identification signal uniquelyidentifies the portable base station to one or more access terminals.

The request from the portable base station may include data thatrepresents the location of the portable base station. The code space mayinclude a sequence of pseudorandom numbers and the assigned code spaceportion may be defined by an offset associated with the sequence. Thisoffset may be represented by one or more types of data such as by anumber of chips. Requesting the assignment may be initiated by apredefined event such as powering up the portable base station or theremotely located control station requesting the status of the portablebase station. The code space may conform to one or more standards andprotocols such as a Code Division Multiple Access (CDMA) standard, aUniversal Mobile Telecommunication System (UMTS) standard, or othersimilar standard.

Among the advantages of the techniques described here are one or more ofthe following.

By dynamically assigning code space (e.g., offsets of a pseudorandomnumber sequence, etc.) to portable base stations, the portable stationsmay be deployed and made operational in a relatively short time periodand in a cost effective manner (compared to the time-consuming,deliberate and often expensive exercise of manual code spaceassignment). Additionally, by requesting the assignments from a controlstation, code space assignments may be tracked by the control stationalong with the location of the portable base stations. Furthermore,predefined events may initiate assignment requests, thereby, providingmore controllability in allocating the code space.

Other features and advantages will be apparent from the description andthe claims.

DESCRIPTION

FIG. 1 is a diagram of a telecommunication core network in communicationwith a fixed location base station and a portable base station.

FIG. 2 is a diagram of a control station in communication with multipleportable base stations and a fixed location base station.

FIG. 3 is a diagram of a PN sequence.

FIG. 4 is a flow chart of operations executed by an Offset Assigner.

FIG. 5 is a flow chart of other operations executed by an OffsetAssigner.

Referring to FIG. 1, a radio access network (RAN) 100 includes aconventional antenna tower 102 that is erected at a fixed location andtransmits and receives electromagnetic signals that are provided to orfrom a fixed location base station 104. One or more signaling techniquesand standards may be implemented by the fixed location base station 104to establish communication links (via the antenna tower 102) with one ormore ATs such as a cellular telephone 106. For example, techniques andstandards associated with the Universal Mobile Telecommunications System(UMTS) may be implemented such that multiple ATs may establishcommunication links and access the fixed location base station 104.Standards associated with spread spectrum air interface protocols suchas code division multiple access (CDMA), wideband (W-CDMA), etc. mayalso be implemented for multiple AT access.

Other protocols supported may include the 1×EV-DO protocol, which is anEVolution of the 1×RTT standard for high-speed data-only (DO) servicesand has been standardized by the Telecommunication Industry Association(TIA) as TIA/EIA/IS-856, “CDMA2000 High Rate Packet Data Air InterfaceSpecification”, 3GPP2 C.10024-0, Version 4.0, Oct. 25, 2002, which isincorporated herein by reference. Revision A to this specification hasbeen published as TIA/EIA/IS-856, “CDMA2000 High Rate Packet Data AirInterface Specification”, 3GPP2 C.S0024-A, Version 2.0, June 2005, whichis also incorporated herein by reference. Revision B to thisspecification has been initiated as TIA/EIA/IS-856, “CDMA2000 High RatePacket Data Air Interface Specification,” 3GPP2 C.S0024-B, Version 1.0,March 2006 and is also incorporated herein by reference.

To identify itself, the fixed location base station 104 transmits asignal (via the antenna 102) that uses one or more spread spectrumtechniques such as being modulated with a unique pseudorandom code.Thereby, the identification signal may appear as noise, however, thesignal may be extracted with a correlation process by an appropriatereceiver aware of the pseudorandom sequence. By implementing such spreadspectrum techniques or orthogonal coding techniques, an AT maydistinguish base station identities and the probability ofidentification signal interference may be reduced. Other types oforthogonal or non-orthogonal coding techniques may also be used toproduce unique transmission signals. For example, different PN sequences(e.g., gold sequences) referred to as scrambling codes (for W-CDMA) maybe implemented. Different types of information may also be transmittedto uniquely identify the base station 104. For example data (e.g., acell identifier) uniquely assigned to the base station 104 may betransmitted.

To provide an identification signal (along with transmitting andreceiving other signals), the fixed location base station 104 includes aradio node (RN) 108 that supports the wireless standards and protocols(e.g., CDMA, W-CDMA, UMTS, etc.) for communicating with the ATs.Typically the RN 108 includes a transceiver for receiving andtransmitting electromagnetic signals. The RN 108 may also include one ormore components (e.g., a modulator/demodulator (MODEM)) for modulating atransmission carrier signal to encode digital information fortransmission or demodulating a received analog signal to decodetransmitted digital information. The RN 108 is connected to a radio nodecontroller (RNC) 110 that provides commands (and transmission signals)to the RN 108 and receives incoming signals from the RN 108. An accessgateway 112 such as a packet data serving node (PDSN) is connected tothe RNC 110 and may be implemented as a data server to direct datapackets to appropriate delivery locations. Additionally the accessgateway 112 provides an interface between networking functions andservice levels defined by one or more standards such as the Open SystemsInterconnect (OSI) protocol standard defined by the InternationalStandards Organization (ISO), which is herein incorporated by reference.With reference to the seven OSI protocol layers, the access gateway 112provides an interface between the link layer (e.g., layer 2)functionality provided by the fixed location base station 104 and therouting layer (e.g., layer 3) functionality provided by a core network114 that is connected to the fixed location base station. Along withsending and receiving content (e.g., data packets) to and from the fixedlocation base station 104, the core network 114 exchanges data andsignals with other components included in the RAN 100. For example, datamay be sent to other base stations, conventional landline telephonesystems (e.g., Plain Old Telephone Service (POTS) systems, etc.) orother similar delivery sites and sources.

As mentioned above, antenna towers such as antenna tower 102 are erectedto remain fixed at one location. Prior to erecting the towers, thegeographical layout of the towers is planned to provide wirelesscoverage. Additionally each tower is assigned a portion of a code spaceso that the antenna (and corresponding fixed location base station 104)may uniquely identify itself to the one or more ATs within the coveragearea. Since ATs such as AT 106 communicate with base stations (e.g.,CDMA, W-CDMA and UMTS base stations) on the equivalent frequencies, anAT needs to differentiate one fixed location base station from another.In order to identify each fixed location base station separately, eachbase station repeatedly transmits an identical pseudorandom number (PN)sequence of codes that are offset in time from the PN sequences beingtransmitted by the other base stations. The PN offset is assigned toeach fixed location base station respectively connected to an antennaerected at a fixed location. Typically these offset assignments aredetermined prior to the antenna tower becoming operational and arestatic in the sense of not being adjusted once the tower is inoperation. However, such a manual offset assignment process is oftentime-consuming and expensive. Different PN-sequences may also betransmitted to uniquely identify base stations. Furthermore, signals maybe transmitted on different frequencies or share a similar frequency.

The RAN 100 also includes a portable base station 116 that is incommunication with the core network 114 and provides the functionalityof the fixed location base station 104. For example, the portable basestation 116 includes an RN 118, an RNC 120 and an access gateway 122(e.g., a PSDN). The portable base station 116 is connected to a portableantenna 124 that is capable of establishing links with one or more ATs,however, antenna characteristics (e.g., beam pattern, gain, etc.) of theportable antenna are typically selected for establishing links to ATslocated relatively close to the portable base station. Furthermore, thedesign characteristics (e.g., component size, power consumption, etc.)of the RN 118, RNC 120 and the access gateway 122 may be selected forportability. As such, the portable base station 116 may provide lesswireless coverage area than the fixed location base station 104 (e.g.,coverage to service a single residential home, a portion of a multipleresidence building or other structure or location of similar size andarea). However, due to its mobility, the portable base station 116 mayinterfere with the operations of the fixed base station 104 or otherrelatively closely located base stations (e.g., other portable basestations, fixed location base stations). For example, identificationsignals using near-by or equivalent code space (e.g., PN offset, PNsequence, etc.) may interfere with the identification signalstransmitted by the portable base station 116.

Referring to FIG. 2, a RAN 200 includes three portable base stations202, 204, 206 that are respectively located at and provide coverage tothree separate locations (e.g., residential homes) 208, 210, 212. TheRAN 200 also includes a fixed base station 214 that is connected to anantenna tower 216 that also provides wireless coverage (e.g., largercoverage than the portable base stations). Each of the portable basestations 202, 204, 206 and the fixed base station 214 are connected to acore network 218 that is in communication with a control station 220(e.g., remotely located from the locations 208, 210 and 212) thatincludes a server 222 or other type of computing device (e.g., acomputing system) or multiple computing devices that may providedistributed processing. The server 222 is in communication with astorage device 224 (e.g., magnetic, magneto-optical disks, or opticaldisks, etc.) that stores files, data structures, applications andinstructions for execution by the server, or other types of data.

Due to their mobility, two or more of the portable base stations 202,204, 206 may be closely located to each other (or to the fixed tower216) and transmit identification signals on different or equivalentfrequencies. As such, an AT 226 may be unable to distinguish between thepair of portable base stations (or a portable base station and the fixedtower 216). For example, locations 210 and 212 may be closely located(e.g., adjacent rooms, apartments, etc.) and the AT 226 may detectidentification signals from both of the portable base stations 204 and206. In particular, if the PN offsets or PN sequences (used by theportable base stations 210 and 212) are similar (e.g., occupy nearbycode space or equivalent code space), the AT 226 may be unable todistinguish between the identification signals. In another scenario,additional portable base stations (using similar code space) may bemoved into the area (e.g., placed in adjacent rooms or the same room)and may not be distinguishable by the AT 226.

By assigning PN offsets (or different PN sequences) dynamically to eachportable base station, code space may be allocated in a cost effectiveand timely manner (as each station is deployed). Furthermore, dynamicallocation allows distinguishable identification signals to betransmitted (using different or equivalent frequencies) from closelylocated portable base stations, thereby reducing potential signalcollisions. For example, PN offsets widely separated in a PN sequencemay be assigned to closely located portable base stations (or the fixedtower base station and a portable base station). As the portable basestations are moved (e.g., from one residence to another), the PN offsetassignments may be adjusted to reduce potential identification signalcollision. For example, by tracking the locations (e.g., GlobalPositioning System (GPS) coordinates) of the portable base stations andthe fixed location base stations, a code space may be segmented andassigned for minimal interference among the base stations.

In the exemplary RAN 200, the control station 220 (via communicationwith the core network 218) dynamically allocates code space (e.g., oneor more PN sequences) and assigns portions of the code space (e.g., PNoffsets, PN sequences, etc.) to each of the portable base stations 202,204, 206 (and optionally, the fixed location base station 214). Locationtracking, PN offset assignment storage, and other functions may also beprovided by the control station 220. In this arrangement, the server 222executes operations for tracking the location of the base stations(e.g., portable base stations, fixed location base stations) and assignsappropriate PN offsets to the base stations based upon the locationinformation and potentially other information (e.g., base stationcapabilities, performance, time of day, etc.). The server 222 stores thecode space assignments along with other information (e.g., base stationlocation information, base station capabilities, assignmentconfirmations, etc.) in the storage device 224. In some implementationstransmissions between the control station 220 and the base stations(fixed or portable) are encrypted to reduce the probability ofinterception or modification. Furthermore, the encryption technique(s)may block base station users from modifying information (e.g., PNoffsets) included in the transmissions.

PN offset (or PN sequence) assignment(s) may be initiated by theoccurrence of a particular event which may or may not be predefined. Forexample, a portable base station may request a PN offset upon becomingoperational (e.g., powered up) and establishing communication with thecore network 218. The request may be provided in one or more forms suchas a signal, electronic message, file, data structure, or other similarform. For illustration, a message 228 is sent by the portable basestation 204 to the control station 220 via the core network 218 uponbeing powered up and establishing a communication link with the corenetwork. In a similar manner the other portable base stations 202, 206may request a PN offset (or other type of code space portion) uponbecoming operational. In addition to becoming operational, events thatinitiate a PN offset request may include the occurrence of predefinedtime (e.g., midnight each evening), resetting the portable base station,user initiated, or other type of event.

The request 228 may contain one or more types of information such asdata that identifies the portable base station 204 (e.g., a uniquealphanumerical identifier assigned to the base station by amanufacturer, etc.), the location of the portable base station (e.g.,GPS coordinates), base stations capabilities (e.g., coverage area,transmission power, etc.), status information (e.g., number ofestablished ATs links) and other types of information. For example, GPScoordinates may be inserted into the message 228 from a GPS receiver(not shown) that is included in the portable base station 204. Locationinformation may also be provided from an external source such as anexternal GPS receiver or other type of location determining device incommunication with the portable base station 204. Data that represents apreviously used PN offset (or other type of code space portion) may alsobe included in the message 228. For example, the last PN offset assignedor a list of previously assigned PN offsets (e.g., all assignments,assignments over a period of time) may be provided in the request. Thesepreviously assigned PN offsets may be used by the server 222 forassigning the requested offset (e.g., assign a new PN offset, assign apreviously used PN offset, etc.). In some arrangements, preference mayfactor into some assignments as described in “Configuring Preferred UserZone Lists for Private Access Points for Wireless Networking”, U.S.patent application Ser. No. ______, filed on 15 Dec. 2006, the entirecontents of which are hereby incorporated by reference. Information suchas location information may be provided to the portable base station 204from a user interface (e.g., a keyboard) or a data conduit (e.g.,communication port) from another device (e.g., a GPS receiver). Otherincluded information may be used for security (e.g., a public key,etc.), data compression, or other types of functions.

Rather than the portable base station 204 initiating a request, thecontrol station 220 may trigger a request for a PN offset assignment.For example, a polling signal may be sent from the control station 220to each of the base stations (portable and fixed location) at predefinedintervals (e.g., daily, weekly, etc.). Upon receiving the pollingsignal, requests such as the request 228 may be produced and sent fromthe corresponding portable base station 204 to the control station 220.Along with polling all of the portable and fixed location base stations,in some arrangements a portion of the base stations may be polled. Forexample, based stations located in a particular geographical region maybe polled at one time and base stations located in another region may bepolled at a different time. In another scenario, the server 222 maytrack mobile base stations that are more frequently assigned PN offsets(e.g., due to frequent movements). These base stations may be polledmore frequently than base stations that have a relatively stationaryhistory.

To process the received requests, an Offset Assigner 230 is executed bythe server 222. Along with request processing, the Offset Assigner 230identifies the appropriate PN offset (if any) that should be assignedand informs the base station of the assignment. For example, upondetermining a PN offset assignment for the portable base station 204, amessage 232 is sent from the control station 220 to the portable basestation. Data 234 represents the PN offset that may be retrieved fromthe message 232 and stored in a memory (not shown) (e.g., random accessmemory (RAM), read-only memory (ROM), static RAM (SRAM), etc.) or astorage device (also not shown) included in the portable base station204. Similarly, the control station 220 may respectively provide PNoffsets 236, 238 to the other portable base stations 202, 206. While thefixed location base station 214 is typically assigned a PN offset basedupon a planning procedure that is executed prior to the tower 216becoming operational, in some scenarios the control station 220 mayassign a PN offset 240 to the fixed location base station. The assignedPN offset 240 may be used by a MODEM, which is included in the RNportion of the fixed location base station 214, to produce anappropriate identification signal.

As PN offsets are assigned, the server 222 stores data that representsthe offset assignments. For example, data may be stored in the storageunit 224 that uniquely represents both the assigned offset and the basestation to which it is assigned. One or more data types, datastructures, storage techniques and methodologies may be implemented sothat the assigned offsets may be efficiently stored and retrievable.

One or more techniques and methodologies may be used by the OffsetAssigner 230 to determine PN offset assignments. For example, by usinglocation information included from the request messages, the OffsetAssigner 230 may use the distance between the base stations indetermining the PN offset assignments. The capabilities of the basestations may also be used in the determination. For example, the rangethat each base station is capable of establishing an AT link may be usedto determine potential signal collision ranges among the base stations.These and other techniques and methodologies, known in the art of signalcollision avoidance, individually or in combination, may be implementedby the Offset Assigner 230.

Referring to FIG. 3, a diagram 300 represents a sequence 302 ofpseudorandom numbers that form one exemplary code space that may beallocated among portable base stations (and fixed location basestations). In this representation the PN sequence 302 includes binarynumbers (e.g., a “0” or a “1”) that occur substantially at random in thesequence. The PN sequence 302 may be generated by implementing one ormore techniques, for example, a random number generator may produce thesequence. Each binary number is referred to as a chip and may beconsidered the basic building element from which the PN sequence isproduced. The length of the PN sequence is referred to as a frame and ispredefined with a relatively large number of chips. For example, thissequence may represent 32,768 chips, however, other exemplary sequencesmay include more or less chips.

As mentioned, for identification, each portable base station maytransmit the sequence as an identification signal within its coveragedistance. To provide a continuous signal, the sequence is transmitted ina repetitive manner from each base station. Each portable base stationtransmits a unique identification signal to differentiate itself fromother base stations. For example, each portable base station mayinitiate transmission of the sequence 302 starting from a different chipincluded in the sequence. Each starting chip may be identified bydividing the frame into a predefined number of segments. For example,the frame may be divided into segments with equivalent chip lengths(e.g., sixty-four chips). As such, the frame (with a length of 32,768chips) is divided into 512 segments that each include 64 chips.Alternatively, segments lengths may not be equivalent and some maycontain different number of chips.

In the figure, the first chip of each segment is identified as anoffset. For example, “Offset 1” identifies the first chip of the firstsixty-four chip segment, “Offset 2” identifies the first chip of thenext sixty-four chip segment and “Offset 3” identifies the first chip ofthe next following segment. In this example, the final sixty-four chipsegment starts with a chip identified by offset 512 (not shown). While asixty-four chip segment is used in this illustration, segment length maybe longer or shorter.

Factors such as the number of portable (and fixed location) basestations may influence frame segmentation. For example, for a largeamount of base stations, the frame may be segmented to provide manyoffset values. Alternatively, for fewer base stations, the frame may besegmented to provide fewer offsets (with wider separations).Furthermore, frame segmentation may be time dependent. For example, forcertain time periods (e.g., during the day, week, etc.) the frame may besegmented to provide a particular number of offsets for base stationassignments. Then, at another time period, the frame may be re-segmentedto provide more or less offsets. In other scenarios, segmenting may beinitiated by the occurrence of an event. For example, the number ofportable base stations located at a particular location (e.g., asporting event stadium) may increase based on a predefined event (e.g.,a sporting event). The frame may be divided to provide additionaloffsets during the event and upon the completion of the event, the framemay be re-segmented to provide less offsets since less portable basesstations may be present at the location.

Various types of information such as RAN level factors (e.g., the numberof base stations, base station separation distances, etc.), base stationspecific information (e.g., transmission and reception capabilities),performance metrics (e.g., collision probability) and other informationmay also influence offset assignment. For example, two portable basestations (e.g., base station 204 and 206) that are separated by arelatively small distance may be respectively assigned offsets (e.g.,offset 1 and offset 512) separated a considerable distance in the frame.Generally, the probability of collision reduces as offset separationincreases. Also, design, performance and calibration metrics may berelaxed with increased offset separation. For example, for widelyseparated PN offsets, timing calibration may be relaxed. So, rather thanfrequently monitoring a highly accurate timing signal (e.g., a timingsignal from a GPS system) to calibrate one or more internal clocks, abase station may use a less accurate timing reference signal, e.g., froma core network (or other timing source). Furthermore, timing calibrationcycles may occur less frequent for base stations using widely separatedoffsets. Due to this calibration relaxation, less accurate and lessexpensive components may be used to produce the base stations.Similarly, reducing the number of frame segmentations (e.g., from 512 to256), increases offset separation and thereby reduces the probability ofsignal collision.

Characteristics of the PN sequence may be selected to agree with one ormore standards and protocols. For example, the frame length and framesegmentation may be selected to conform with a standard. A CDMA framehas a predefined length of 32,768 chips while a UMTS frame has a lengthof 40,960 chips. Both CDMA and UMTS frames may be divided into segments(referred to as slots) that are designated for particular channels. Forexample, a CDMA time slot may be defined to include 2048 chips while aUMTS time slot length includes 2560 chips. As such a CDMA frame has 16slots while a UMTS frame has 15 slots. However, the frame length andslot length may vary dependent upon the standards and protocols beingimplemented.

Starting with the chip identified by the offset (e.g., Offset 2)assigned to the portable base station (e.g., portable base station 204),the following chips are sequentially used to produce an identificationsignal. Upon reaching the end of the sequence (e.g., chip 32768), theportable base station returns to the beginning of the sequence (e.g.,chip 1) and repetitively uses the sequence. While this particularexample uses a sequence of pseudorandom numbers to define the code spaceand offsets to define segments of the code space, other methodologiesand techniques may be implemented to define and segment a code space.

Referring to FIG. 4, a flowchart 400 represents some of the operationsof the Offset Assigner 230 (shown in FIG. 2). As mentioned above, theOffset Assigner 230 may be executed at the control station 220. Forexample, the server 222, a computer system of other type of computationdevice located at the control station 220 may execute the OffsetAssigner 230. Furthermore, along with being executed at a single site(e.g., control station 220), operation execution may be distributedamong two or more sites. For example, some operations may be executed byone or more of the portable base stations and at the server located atthe control station 220.

Operations of the Offset Assigner 230 include receiving 402 a requestfor an offset assignment from a base station such as a portable basestation (e.g., base station 204) and determining 404 if an offset may beassigned to the base station. For example, the Offset Assigner 230 mayaccess a list of available offsets that is stored in server memory (notshown), the storage device 224 or other type of data storage unit thatis in communication with the server 222. Previously assigned offsets tothe portable base station may also be checked for availability. If nooffsets are available, operations of the Offset Assigner 230 may includedenying 406 the portable base station access to the RAN. The OffsetAssigner 230 may also send a signal or message to inform the portablebase station of the lack of offset availability and possibly provide anestimated time in which availability may improve.

If one or more offsets are available, operations include determining 408if an offset had been previously assigned to the portable base station.For example, the request from the portable base station may include datathat represents that one or more offsets had been previously assignedand the Offset Assigner 230 may check data stored in the server, thestorage device, or other device to identify any previously assignedoffsets. The server may also request additional information from theportable base station to identify the offsets. For example, the servermay send a message to the portable base station that includes a requestfor any previous offsets assigned to the base station.

If an offset had not been previously assigned, operations includeassigning 410 an available offset to the portable base station. Asmentioned above, the offset assignment may use one or more factors. Forexample, the approximate location of the portable base station alongwith the location of other base stations (portable and fixed location)near by (or remotely located) to the portable base station may be usedto determine the assigned offset. Operational characteristics of one ormore base stations (portable and fixed location) may also be used. Forexample transmission power, coverage area (e.g., number of coveragesectors), antenna beam patterns, etc. may be used to identify anappropriate offset for assignment.

In this implementation, if an offset had been previously assigned to theportable base station, operations include determining 412 if theprevious assignment may be reused. For example, the Offset Assigner 230may check presently assigned offsets to determine if the previousassignment is currently being used by another base station. If thepreviously assigned offset is unavailable, operations include assigning410 an available offset to the portable base station. If the previousassignment is available, the Offset Assigner 230 may re-assign theoffset to the base station. Whether re-assigned or newly assigned,operations also include storing 414 the offset assignment for laterretrieval and use. Typically, data that identifies the offset assignmentand the portable base station are stored in memory, storage device 222,or other type of storage unit. Data structures and files along with datastorage techniques and methodologies may be implemented to store theinformation.

Referring to FIG. 5, a flow chart 500 represents operations in which theOffset Assigner 230 monitors the offset assignments and dynamicallyadjusts the assignments, as needed. As the portable base stations aremoved (e.g., enter areas, leave areas, etc.) from location to location,the probability of collisions may increase if two or more closelylocated bases stations can not be distinguished by one or more ATs inthe general vicinity. By monitoring the status (e.g., location,operability, etc.) of the portable base stations in communication withthe server 222, the Offset Assigner 230 may update offset assignments inan efficient (and cost effective) manner, and thereby to reduce theprobability of collisions. For example, as a portable base station ismoved near (e.g., into the same building) to a group of other portablebase stations, offsets may be adjusted to reduce conflictingassignments. In some implementations, the portable base stations mayperiodically send messages to the control station 220 that includestatus information (e.g., location, operability, etc.), or, the controlstation 220 may solicit status information from portable base stations.For example, the server 220 may send or broadcast a message to eachportable base station. As such, operations of the Offset Assigner 230may include sending 502 a status request to each portable base station(and optionally, to each fixed location base station). In response toreceiving the status request, the portable base stations may send amessage to the control station 220 that includes status information. Insome scenarios, one or more responses may be delayed due to currentactivities or non-activity of the base station. For example, ifcurrently providing service to an AT, a base station may not be able tosend a response until service operations are complete or sufficient basestation processing resources become available. Base stations that arenot operating (e.g., powered down) typically are unable to send aresponse to answer the control station 220 request. In somearrangements, delayed responses and lack of responses are tracked by thecontrol station 220 and may factor into the offset assignments.

Operations also include receiving 504 one or more base station responsesand determining 506 if the offset assignment(s) should be updated. Alongwith changes in location, changes in operability and the introduction ofone or more new portable base stations, the Offset Assigner 230determines if one or more offset assignments should be updated. Forexample, assignments may be deleted, added, or changed based upon thereceived responses.

If determined that the current assignments are satisfactory (e.g., dueto minimal changes in deployment locations, meeting a predefinedcollision probability threshold, satisfying a metric, etc.), the OffsetAssigner 230 may maintain 508 the offset assignment(s). In someimplementations operations may also include recording this determinationfor statistical or other analysis. If assignment updates are warranted,operations include re-assigning 510 the offsets as appropriate. Forexample, portable base stations may be assigned offsets based uponmoving to different locations, to reduce the probability of collision(e.g., separate the offset distances), etc., or, new offset assignmentsmay be identified and sent to the corresponding base stations. TheOffset Assigner 230 also stores 512 the offset re-assignments, forexample, in the storage device 224 for later retrieval and use.

The Offset Assigner 230 may also monitor other operations and eventsassociated with the base stations. For example, PN offsets, PN sequencesor other types of code space portions used in base station transmissionsmay be monitored. By monitoring the transmissions, the Offset Assigner230 may compare the code space portions (used in transmissions) to theassigned portions of code space. If a match is detected, thetransmissions may be allowed to continue. If a match is not detected,one or more signals or commands may be sent from the control station 220to halt transmission from the respective base station. Accordingly, theproperly assigned code space portion may then be provided to the basestation for use in identification transmissions.

In some embodiments one or more processors may execute instructions toperform the operations of the Offset Assigner 220, e.g., respectivelyrepresented in flowchart 400 and 500. For example, one or more generalprocessors (e.g., a microprocessor) and/or one or more specializeddevices (e.g., an application specific integrated circuit (ASIC), etc.)may execute instructions. One or more of the processors may beimplemented in a single integrated circuit as a monolithic structure orin a distributed structure. In some embodiments the instructions thatare executed by the processors may reside in a memory (e.g., randomaccess memory (RAM), read-only memory (ROM), static RAM (SRAM), etc.).The instructions may also be stored on one or more mass storage devices(e.g., magnetic, magneto-optical disks, or optical disks, etc.).

One or more of the operations associated with the Offset Assigner 220may be performed by one or more programmable processors (e.g., amicroprocessor, an ASIC, etc.) executing a computer program. Theexecution of one or more computer programs may include operating oninput data (e.g., data provided from a source external to the RAN, etc.)and generating output (e.g., sending data to a destination external tothe RAN, etc.). The operations may also be performed by a processorimplemented as special purpose logic circuitry (e.g., an FPGA (fieldprogrammable gate array), an ASIC (application-specific integratedcircuit), etc.).

Operation execution may also be executed by digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The operations described in flowcharts 400 and 500(along with other operations of the Offset Assigner 220) may beimplemented as a computer program product, e.g., a computer programtangibly embodied in an information carrier, e.g., in a machine-readablestorage device (e.g., RAM, ROM, hard-drive, CD-ROM, etc.) or in apropagated signal. The computer program product may be executed by orcontrol the operation of, data processing apparatus, e.g., aprogrammable processor, a computer, or multiple computers. A computerprogram may be written in one or more forms of programming languages,including compiled or interpreted languages, and it can be deployed inany form, including as a stand-alone program or as a module, component,subroutine, or other unit suitable for use in a computing environment. Acomputer program may be deployed to be executed on one computing device(e.g., controller, computer system, etc.) or on multiple computingdevices (e.g., multiple controllers) at one site or distributed acrossmultiple sites and interconnected by a communication network.

Other embodiments are within the scope of the following claims.

1. A method comprising: a portable base station, requesting assignmentof a portion of a code space from a remotely located control station,wherein the assignment is based, at least in part, upon the location ofthe portable base station; and transmitting an identification signalfrom the portable base station, using the assigned code space portion,to uniquely identify the portable base station to one or more accessterminals.
 2. The method of claim 1 in which the request from theportable base station includes data that represents the location of theportable base station.
 3. The method of claim 1 in which the code spaceincludes a sequence of pseudorandom numbers.
 4. The method of claim 3 inwhich the assigned code space portion is defined by an offset associatedwith the sequence of pseudorandom numbers.
 5. The method of claim 4 inwhich the offset is defined by a number of chips.
 6. The method of claim1 in which requesting the assignment is initiated by a predefined event.7. The method of claim 6 in which the event includes powering up theportable base station.
 8. The method of claim 6 in which the eventincludes the remotely located control station requesting the status ofthe portable base station.
 9. The method of claim 1 in which the codespace conforms to a Code Division Multiple Access (CDMA) standard. 10.The method of claim 1 in which the code space conforms to a UniversalMobile Telecommunication System (UMTS) standard.
 11. A systemcomprising: a portable base station to request assignment of a portionof a code space from a remotely located control station, wherein theassignment is based, at least in part, upon the location of the portablebase station, the portable base station is also capable of transmittingan identification signal by using the assigned code space portion touniquely identify the portable base station to one or more accessterminals.
 12. The system of claim 11 in which the portable base stationprovides the functionality of a radio node, a radio node controller andan access gateway.
 13. The system of claim 11 in which the assignment isbased upon the distance between the portable base station and anotherbase station.
 14. The system of claim 11 in which the remotely locatedcontrol station includes a server to assign the code space portion. 15.The system of claim 11 in which the assignment request includes datathat represents the location of the portable base station.
 16. Thesystem of claim 11 in which the code space includes a sequence ofpseudorandom numbers.
 17. The system of claim 16 in which the assignedcode space portion is defined by an offset associated with the sequenceof pseudorandom numbers.
 18. The system of claim 17 in which the offsetis defined by a number of chips.
 19. The system of claim 11 in which theassignment is requested upon the occurrence of a predefined event. 20.The system of claim 19 in which the event includes powering up theportable base station.
 21. The system of claim 19 in which the eventincludes the remotely located control station requesting the status ofthe portable base station.
 22. The system of claim 10 in which the codespace conforms to a Code Division Multiple Access (CDMA) standard. 23.The system of claim 10 in which the code space conforms to a UniversalMobile Telecommunication System (UMTS) standard.
 24. A medium bearinginstructions to cause: a portable base station to request assignment ofa portion of a code space from a remotely located control station,wherein the assignment is based, at least in part, upon the location ofthe portable base station; and transmission of an identification signalfrom the portable base station by using the assigned code space portion,wherein the identification signal uniquely identifies the portable basestation to one or more access terminals.
 25. The medium of claim 24 inwhich the assignment request from the portable base station includesdata that represents the location of the portable base station.
 26. Themedium of claim 24 in which the assigned code space includes a sequenceof pseudorandom numbers.
 27. The medium of claim 26 in which theassigned code space portion is defined by an offset associated with thesequence of pseudorandom numbers.
 28. The medium of claim 27 wherein theoffset is defined by a number of chips.
 29. The medium of claim 24wherein requesting the assignment is initiated by an event.
 30. Themedium of claim 29 wherein the event includes powering up the portablebase station.
 31. The medium of claim 29 wherein the event includes theremotely located control station requesting the status of the portablebase station.